The present invention relates generally to active metal electrochemical devices. More particularly, this invention relates to protected anodes architectures incorporating compliant seal structures, including single and double sided protected anodes and arrays of protected anodes, and their associated electrochemical cell structures and devices such as batteries, particularly, active metal/air batteries and active metal/seawater batteries, and methods for their fabrication.
The low equivalent weight of alkali metals, such as lithium, makes them particularly attractive as a battery electrode component. Lithium provides greater energy per volume than the traditional battery standards, nickel and cadmium. Unfortunately, no rechargeable lithium metal batteries have made significant penetration in the market place.
The failure of rechargeable lithium metal batteries is largely due to cell cycling problems. On repeated charge and discharge cycles, lithium “dendrites” gradually grow out from the lithium metal electrode, through the electrolyte, and ultimately contact the positive electrode. This causes an internal short circuit in the battery, rendering the battery unusable after a relatively few cycles. While cycling, lithium electrodes may also grow “mossy” deposits that can dislodge from the negative electrode and thereby reduce the battery's capacity.
To address lithium's poor cycling behavior in liquid electrolyte systems, some researchers have proposed coating the electrolyte facing side of the lithium negative electrode with a “protective layer.” Such protective layer must conduct lithium ions, but at the same time prevent contact between the lithium electrode surface and the bulk electrolyte. Many techniques for applying protective layers have not succeeded.
Some contemplated lithium metal protective layers are formed in situ by reaction between lithium metal and compounds in the cell's electrolyte that contact the lithium. Most of these in situ films are grown by a controlled chemical reaction after the battery is assembled. Generally, such films have a porous morphology allowing some electrolyte to penetrate to the bare lithium metal surface. Thus, they fail to adequately protect the lithium electrode.
Prior work in the present applicants' laboratories has developed technology for protecting active metal anodes with highly ionically conductive protective membrane architectures. These protected active metal anodes structures and associated electrochemical cells, described in applicants' co-pending published US Applications US 2004/0197641 and US 2005/0175894, and their corresponding International Patent Applications WO 2005/038953 and WO 2005/083829, respectively, represent major advances in active metal battery technology, for instance rendering possible functional Li/air and Li/water batteries. This technology would be further advanced by the development of seal structures and techniques that would facilitate and/or optimize the implementation of these protected active metal anode structures.